I just found out that you can turn a specific sprite into the icon for the binary export: https://www.lexaloffle.com/dl/docs/pico-8_manual.html#Binary_Applications_ and whoa, this is really great! But afaict it's restricted to the standard palette. Is there some way to set a custom palette for the icon in the export? If not, adding some sort of palette flag might be a nice feature:

EXPORT -I 32 -C 12 -Z 0,132,4,140,134,6,135,7,8,137,139,11,138,130,13,131 MYGAME.BIN

or maybe reuse the -C flag, and a -1 entry means transparent?

EXPORT -I 32 -C 0,132,4,140,134,6,135,7,8,137,139,11,-1,130,13,131 MYGAME.BIN

(although that might be a bit awkward because using pal(12,-1,1) ingame means to map 12->0x8F, not 12->transparent...)